The present invention relates to the construction of composite preform structural panels, and more particularly to a composite preform incorporating an electrically conductive stitching that forms an electrically conductive grid network to dissipate electrical energy received from a lightning strike throughout the thickness of the composite preform structural panel.
The ability to effectively deal with lightning strikes on composite materials that form structural panels for wings, fuselages and other components of a primary aircraft structure is anticipated to be an important consideration on newly developed aircraft. This is because composite materials, which are becoming increasingly common in aircraft use, are not highly conductive and cannot readily dissipate the energy from a lightning strike as efficiently as the traditional metal body components used with many present day primary aircraft. Composite materials are nevertheless highly desired because of the significant weight reduction that they can provide, in addition to the very high structural rigidity and strength they offer.
Presently, the solution to providing composite materials with the ability to dissipate electrical energy experienced during a lightning strike has involved coating the composite body panels with coatings such as Astrostrike(copyright) or other like materials. Such a solution forms an additional manufacturing step that is required to be performed after the composite preform, that forms the aircraft structural panel, has been completely manufactured. This is obviously more expensive than a solution in which the composite preform forming the structural panel is manufactured to include a means to dissipate electrical energy from a lightning strike.
It would therefore be highly desirable to provide a composite preform structural panel, as well as a manufacturing process, that integrates lightning protection directly into the primary manufacturing process of the composite preform. More specifically, it would be highly desirable to provide a structural panel and method of manufacturing same in which lightning protection is integrated into the primary manufacturing process in a manner that does not significantly increase the overall weight of the finished composite preform, and which does not significantly add to the cost or complexity of the manufacturing process of forming same.
The above and other objects are provided by a structural panel and method incorporating a stitched, electrically conductive material that is applied to a composite preform during the primary manufacturing process of the composite preform. The apparatus forms a composite preform having electrically conductive stitching that forms a grid-like network for dissipating electrical energy throughout at least a portion of the thickness of the composite preform. In one preferred form, the composite preform includes electrically conductive stitching extending only partially through its thickness. An alternative embodiment incorporates the electrically conductive stitching extending completely through the thickness of the composite preform to opposing surfaces of the composite preform. In yet another preferred form the electrically conductive stitching extends only through a portion of the thickness of the composite preform while a non-conductive polymer stitching extends through the entire thickness of the preform. In either event, the electrically conductive stitching is applied during the primary manufacturing process of forming the structural member.
In each of the preferred embodiments discussed above, the electrically conductive stitching comprises a metal stitching comprised of a metallic thread. In one alternative preferred embodiment suitable for use with fuel tanks and other liquid-containing components, a non-conductive, liquid-crystal polyester stitching is employed as the stitching thread. In one preferred form the non-conductive stitching thread comprises Vectran(copyright) liquid-crystal polymer thread.
The apparatus and method of the present invention forms a means to better dissipate the electrical energy imparted to the composite preform during a lightning strike by using the electrically conductive stitching to dissipate the electrical charge throughout at least a portion of the thickness of the composite preform. Since the electrically conductive stitching is applied during the primary manufacturing process for the composite preform, this significantly reduces the cost associated with the manufacture of the composite preform.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limited the scope of the invention.